EP Test 3 Ch 8

At the start of exercise when the lung expands (increased volume) and V̇E rises, the

airways open up.

There are a variety of laboratory and non-laboratory methods that can be used to identify VT1 and VT2. The ventilatory equivalent for oxygen is the ______________________________. A ratio of V̇E/V̇O2, it provides a good indication of _____________________

amount of V̇E required to consume one liter of oxygen breathing efficiency during exercise and can be used to identify VT1.

The ventilatory equivalent for carbon dioxide is the

amount of V̇E required to expire one liter of CO2.

The point (or exercise intensity) at which V̇E first breaks from linearity with respect to oxygen uptake (expressed as %V̇O2 max) is termed the

first ventilatory threshold (VT1).

Q can increase _____ times above resting values which means that

five to eight (25-40 L/min at maximal exercise), the heart can recirculate its total blood volume significantly every minute with increasing exercise intensity.

Increased body temperature that accompanies prolonged exercise may stimulate

heat sensitive receptors in the hypothalamus to increase RR.

Drifting of V̇E is due primarily to the

increased respiratory rates that accompany high intensity exercise.

For maximum gas exchange to occur, there must be .

proper matching of pulmonary blood flow to alveolar ventilation

As exercise duration increases at a constant workload, bronchodilation and the reduction in airway resistance remain

relatively stable.

Cardiac output it made up of

stroke volume and heart rate

Pulmonary Ventilation

(V̇E)

The immediate changes that occur at the onset of exercise are governed by:

-increased output from the motor cortex in the brain that directs the cardiovascular control -respiratory control centers located in the medulla

The increase in V̇E at the onset of exercise (within the first minute) is driven by two mechanisms:

1) increased tidal volume (VT), and 2) a slightly increased respiratory rate (RR).

The increase in blood pressure at the start of exercise is driven primarily by:

1. Increased sympathetic vasoconstriction of veins and arterioles 2. Reduced parasympathetic activity to the heart and blood vessels 3. An abrupt increase in Q

The metabolic demand for oxygen can rise

15 to 20 times during exercise.

Typical maximal values for SBP range from

160 to 220 mm Hg.

SV increases in proportion to the exercise intensity, but for most people, SV will reach a maximum value at approximately

40% to 60% of VO2max.

Plasma volume can be increased up to End-diastolic volume and preload will be augmented, providing more stretch to the myocardium prior to blood ejection. Increases the force of contraction, enhancing SV, allowing for a decrease in HR, and permitting the heart to be more efficient at maintaining Q at rest

500 mL or more by training.

allows the alveoli to expand during inspiration.

Alveolar interdependence

why we can donate a lung to someone or walk around with a collapsed lung

Arterial partial pressure of oxygen (PO2) and carbon dioxide (PCO2) deviate very little from rest to steady-state exercise

the relationship between stroke volume and heart rate

As one goes down, the other has to go up to maintain the same cardiac output

Talk test (when is VT1 and VT2 identified?)

As the intensity of exercise becomes more difficult and approaches levels close to the ventilatory threshold, talking will become more uncomfortable. The intensity of the exercise bout that reflects the point when talking first becomes uncomfortable identifies VT1. As exercise intensity progressively becomes harder above VT1, speaking is possible, but it will become even more uncomfortable. The point in the exercise bout when talking is clearly difficult (e.g., gasping for air while trying to talk) identifies VT2.

stretch (pressure) receptors located in the heart, carotid sinus, aortic arch, and other major arteries throughout the circulation.

Baroreceptors

at the onset of exercise, the blood pressure set point at which the baroreceptors have been established is raised from its resting state, allowing blood pressure and HR to rise abruptly.

Baroreflex—

If you lift weights, heart rate will get bigger, but heart rate will not really increase so the heart grows but it doesn't say that the heart need to supply more aerobic fuel so it leads to a larger muscle without more blood supply

Cardiac Hypertrophy

gives that initial drive to make everything go faster and then sensory information takes over

Cerebral cortex

remains stable (~70-80 mm Hg) at the onset of cardiorespiratory exercise,

DBP

How is heart rate determined

Determined by the SA node

Increased sympathetic nervous system activity causes

HR and SV (due to increased myocardial contractility) to rise.

Many other stretch receptors appear to exist throughout the peripheral areas of the body that act to increase activity of the cardiorespiratory system during exercise. These receptors may influence

HR, SV, Q, blood pressure, and V̇E during exercise. Hering-Breuer reflex

Not to be confused with the chemoreceptors located in the aortic and carotid bodies, these receptors exert control of

HR, blood pressure, vascular resistance, and cardiac contractility through negative feedback to the cardiovascular control center.

a reflex triggered to prevent over-inflation of the lung. Pulmonary stretch receptors present in the smooth muscle of the airways respond to excessive stretching of the lung during large inspirations.

Hering-Breuer reflex

Notice that Q remains stable throughout the exercise session. ___________________ combine to increase Q during prolonged exercise.

Increases in HR and SV

What does this mean: If the intensity of the exercise bout progressively increases, HR continues to rise to match increasing demands for oxygen.

It basically means that the height of the curve will increase then go steady again (like running up a hill)

other methods to identify VT1 and VT2

Measuring gas Measuring lactate

aortic and carotid bodies and the central chemoreceptors located in the medulla (function)

Modulate V̇E by supplying the respiratory control center with continuous breath-by-breath information on arterial PCO2, PO2, and blood pH

used to regenerate mitochondrial ATP.

O2

keeps heart rate (HR) below 100 beats per minute while at rest.

Parasympathetic activity

a neural mechanism that helps to regulate HR and BP during exercise

Pressor Response—

A limitation of the cardiovascular system is that it contains a finite amount of blood volume (5-6 L) to be circulated. 3 ways the cardiovascular system can overcome this:

Recirculate blood at a higher rate above resting levels Shunt more blood away from non-active tissues to active tissues through targeted vasoconstriction Extract more oxygen from the blood

help to increase venous return.

Respiratory pump, skeletal muscle pump, and venoconstriction

as exercise duration increases, what does the slope of SV and HR do and Q

SV drifts progressively downward HR drifts progressively upward Q remain stable

also increases abruptly at the start of exercise.

Stroke volume (SV), or the amount of blood ejected by the heart in one beat (mL/beat),

rise at the onset of cardiorespiratory exercise

Systolic blood pressure (SBP), mean arterial pressure (MAP), and pulse pressure (PP)

Local factors within the working muscle (and sympathetic activity) stimulate vasodilation, which lowers

TPR (decreases afterload), facilitating a greater Q.

Caused by a decreased mixed venous oxygen content as arterial oxygen content stays relatively stable

The arterial-venous (a-v) O2 difference

increases in a nonlinear fashion with incremental exercise.

The arterial-venous (a-v) O2 difference

provides the initial drive to increase Q and V̇E at the start of exercise.

The cerebral cortex

When exercise starts:

The parasympathetic system is decreased allowing HR to rise. Activity of the sympathetic nervous system gradually increases. Initial rise in HR is abrupt and occurs within the first few minutes of activity. If the exercise intensity remains constant and below the lactate threshold, HR will reach a plateau (steady-state) and remain relatively stable for the duration of a sub-maximal exercise bout. If the intensity of the exercise bout progressively increases, HR continues to rise to match increasing demands for oxygen.

The build-up of metabolites activates mechanoreceptors and chemoreceptors in the skeletal muscle to elevate blood pressure and HR. By raising blood pressure and HR, a pressor reflex occurs in an attempt to increase Q and skeletal muscle blood flow. ______________ involves a forceful exhalation against a closed glottis, which does not allow air to be exhaled out of the mouth and nose. Greatly increases the intrathoracic pressure, which subsequently adds more to the exaggerated blood pressure response during resistance training

Valsalva maneuver

During long duration sub-maximal exercise of high intensity (e.g., >75% V̇O2max) and exercise in a hot environment,

V̇E drifts progressively upward (increase in V̇E/V̇O2 ratio), despite no change in exercise workload.

What is second wind mean?

When we initially start exercising, the brain doesn't know exactly what we are going to need it just knows that it needs more so it needs sensory information to tell exact amounts so then it takes over and breathing will become less labored because its more custom to what the body needs Not a limiting factor If it occurs within the 2 minute window

The primary chemoreceptors that fine-tune activity of the cardiorespiratory system are the

aortic and carotid bodies and the central chemoreceptors located in the medulla.

Airways in the conducting and respiratory zone

dilate (bronchodilation), which results in decreased airway resistance.

Generally, PO2 remains constant up to maximal exercise levels in most people. In some cases, however, PO2 may decrease significantly, a phenomenon known as

exercise-induced hypoxemia.

TPR decreases during exercise to help

facilitate the delivery of blood and oxygen to the working muscle.

Further increase is a

hypertensive response,

and a failure to increase normally is a

hypotensive response.

Venous return enhances end-diastolic volume, which helps to ____________ SV as exercise intensity increases.

increase

One of the primary stimuli for the gradual increase in V̇E during prolonged exercise is

increased circulating catecholamines (epinephrine and norepinephrine) that stimulate the carotid bodies.

Q increases as a function of

increases in HR and SV.

At low-to-moderate exercise intensities, V̇E gradually

increases linearly and stabilizes once steady-state exercise has been achieved.

another name for VT1 and VT2

ka lactic acid threshold

The most important curve in the life of an endurance athlete

lactic acid thresholds

VT2 is identified as the workload marked by the

lowest V̇E/V̇CO2 ratio.

Mechanoreceptors in the muscles (e.g., muscle spindle and Golgi tendon organ) and joints send output signals to the cardiorespiratory control centers with regard to the intensity of movement, changes in joint movement, pressure, and position. When stimulated during exercise, impulses are relayed to the _________ to modify activity of the cardiovascular and respiratory control centers so that Q and V̇E can be regulated during exercise.

medulla

Also enhances the force of ventricular contraction, leading to a greater SV

neurotransmitter norepinephrine.

Increased SV at the start of exercise is caused by the release of the

neurotransmitter norepinephrine.

If a person continues to exercise at progressively higher exercise intensities above VT1, the bicarbonate buffering system is unable to offset metabolic acidosis. Consequently, the respiratory system compensates by substantially increasing VE beyond that of VT1. Eventually, V̇E continues to increase and reaches a second deviation point, termed

the second ventilatory threshold (VT2), often referred to as the respiratory compensation point.

vessels supplying non-exercising muscles and organs

vasoconstrict.

Blood vessels supplying working muscles

vasodilator

To get the most out of our Q, the sympathetic nervous system and local vasodilators work in concert to redistribute blood flow to where it is needed most:

working muscles, heart, and skin.